1. Field
Embodiments relate to a composite positive electrode active material, an electrode for a lithium secondary battery including the composite positive electrode active material, and a lithium secondary battery.
2. Description of the Related Art
Since the miniaturization, lightness, and high performance of portable electronic communication devices, such as camcorders, mobile phones, and notebooks, have been rapidly progressed, demands for miniaturization and high energy density characteristics of lithium secondary batteries used as power sources for driving these portable electronic communication devices have also been increased. Also, an application range of lithium secondary battery recently becomes extended to an automotive battery and a power source for lithium secondary battery hybrid electric vehicles, and in order to apply lithium secondary batteries to such sectors, improvements in low-temperature/high-temperature characteristics and high capacity power characteristics are not only required, but economic factors of price must also be considered.
In general, a lithium secondary battery is classified as a lithium sulfur battery using a sulfur-based material as a positive electrode active material and a lithium ion battery using lithiated transition metal oxide as a positive electrode active material. Due to the low electrical conductivity of metal oxide used as a positive electrode active material, the lithium ion battery includes a conductive agent for smooth supply of electrons between metal oxides or between an electrode collector and a surface of the positive electrode active material and a binder for fixing these materials to the electrode collector. A configuration between the metal oxide, the conductive agent, and the binder significantly affects battery performance and reliability.
The positive electrode active material is a main component affecting battery performance and safety, and lithium composite metal oxides are used as the positive electrode active material. Recently, a great deal of research into layered oxides among the lithium composite metal oxides has been conducted due to their high capacities. However, with respect to a high-capacity positive electrode active material, yLi2MnO3-(1−y)LiMO2 (0<y<1) lithium metal oxide, it may be difficult to be used as an automotive battery, because lifetime of an electrode, low-temperature/high-temperature stability, and high-rate discharge efficiency may be low.
Accordingly, in order to improve high-rate discharge efficiency and low-temperature/high-temperature stability, oxides for a positive electrode active material, such as a positive electrode active material, in which a surface of yLi2MnO3-(1−y)LiMO2 (0<y<1)-based oxide is coated with lithium transition metal oxide, and layered lithium transition metal oxide, have been suggested. However, technical difficulties in stably obtaining power characteristics in a low-temperature atmosphere remain.